Railtrack Shareholders Action Group, representing big investors, warned that, if this cost an extra 0.5% a year, the post-administration bill would be £150m a year higher. Others put the extra cost at 1%, or £300m a year. If Railtrack's successor has to pay the same rate as the current bonds, the cost soars to £870m. If private funding needs to be £34bn, the bill is even bigger.